Vinyl cleaning - Ultrasonic vs. Walker products

I have been using a Nitty Gritty for ages, and it is a must when you have second hand vinyl. The VPI and other record cleaners which use a cleaning solution and vacuum combinations do the same thing as the basic Nitty Gritty does, just with more convenience, but exact same efficiency.The NG is good enough when you have a low-fi mid-fi system. If you want to make the record super clean, then NG treat it several times! I have an 1812 overture that was an unlistenable wild campfire with some background music, and it has cleaned up to a very dynamic and enjoyable record after cleaning it five times with the NG. (Did not remove ll the noise, but turned  frisby into a playable, and more importantly, enjoyable record.)
When you have a very high resolution system, then you can take advantage of the ultrasound (US) cleaner. I have a DIY US cleaner that I have been using for 5+ years. For a very good system, you can clean 4 records at the same spin, and hear MAJOR improvement, as if they have been NG 3-5 times. In case you have a system with the highest resolving power, then you are kicked back to US one record at a time, and you will hear major improvement VS multiple records sonicated at once, or ran through NG multiple times. If you have a large record collection and a top notch system  then the US cleaner is a must - otherwise you are missing out 90% of your collections potential. For example, a record that sounds quite poorly can clean up to give a superb experience. You do not know what is on the record until it is clean... especially in the bass. With dirty records you are missing out the lowest octave entirely.
That's my experience. (I have an audio buddy, and he had the same experience with US cleaning.)

Ultrasonic is superior.  I learned this from experience and formulated my opinion.  I had a very expensive VPI cleaner top of the line (like 4K), vacuum etc.  It cleaned my records well and I had no complaints.  There was noticeable improvement on some of my used LP purchases.
Then I read a thread on Audiogon not much more than 2 1/2 months ago on the subject of LP cleaning.  An engineer in this group talked about his Digital Ultrasonic Cleaner that he paid $150.00 for and raved about it.  I figured for $150 I didn't have a lot to lose and I'd sell which ever one performed the lesser of the two. 
I bought it.  Instructions were not too good.  I think it's made in China, but the pictures were enough to figure everything out.  I put it to work.  I can do 5 records at a time, no sweat.  It is amazing how clean the ultrasonic has gotten my records.  As it vibrates the water and infiltrates the grooves, it cause tiny particulates to fall to the bottom of the silver tank/pan.  I could see in the bottom of the pan from records I had already cleaned with my VPI, specs of dirt that came loose.  As a bonus I even shined up some of my wife's jewelry using it.  
So now my VPI is up for sale.  I will gladly give you a good price on it if you want to go that route.  Otherwise if you want to go ultrasonic just log on line and type in Digital Ultrasonic Cleaner and see if they still come up.  Good luck.

@normantaylor - are you using more than just distilled water?  Any surfactants or detergents or alcohol in you pr US cleaner?

If you've only got 200 to do, I'd strongly recommend BORROWING a cleaner (either vacuum or ultrasonic), paying the lender a few bucks for its use, and call it a day after you do the cleaning.  Since these are inherited and not a collection you've assembled yourself, you'll probably find that you really like about 20 out of the 200 records, and any expense purchasing a record cleaner will have been wasted.